drm/vkms: Add vblank events simulated by hrtimers

This commit adds regular vblank events simulated through hrtimers, which
is a feature required by VKMS to mimic real hardware. Additionally, all
the vblank event send after pageflip is kept in the atomic_flush
function.

Changes since V1:
 - Compute the vblank timer interval per interruption
 Ville Syrjälä and Daniel Vetter:
 - Removes hardcoded vblank interval to get it from user space

Changes since V2:
 Chris Wilson
 - Removes unnecessary algorithm to compute the next period
 Daniel Vetter:
 - Uses drm_calc_timestamping_constants to get the vblank interval
   instead of calculating it manually
 - Adds disable_vblank helper that turns of crtc
 - Simplifies implementation by using drm_crtc_arm_vblank_event
 - Replaces the code in atomic_begin to atomic_flush
 - Removes unnecessary field in vkms_output

Changes since V3:
 Daniel Vetter:
 - Squash "drm/vkms: Add atomic helpers functions" into the commit that
   handling vblank events simulated by hrtimers
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/7709bba40782ec06332d57fff337797b272581fc.1531359228.git.rodrigosiqueiramelo@gmail.com

drivers/gpu/drm/vkms/vkms_crtc.c

@@ -10,6 +10,60 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
 
+static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
+{
+	struct vkms_output *output = container_of(timer, struct vkms_output,
+						  vblank_hrtimer);
+	struct drm_crtc *crtc = &output->crtc;
+	int ret_overrun;
+	bool ret;
+
+	ret = drm_crtc_handle_vblank(crtc);
+	if (!ret)
+		DRM_ERROR("vkms failure on handling vblank");
+
+	ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer,
+					  output->period_ns);
+
+	return HRTIMER_RESTART;
+}
+
+static int vkms_enable_vblank(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	unsigned int pipe = drm_crtc_index(crtc);
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
+
+	drm_calc_timestamping_constants(crtc, &crtc->mode);
+
+	hrtimer_init(&out->vblank_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	out->vblank_hrtimer.function = &vkms_vblank_simulate;
+	out->period_ns = ktime_set(0, vblank->framedur_ns);
+	hrtimer_start(&out->vblank_hrtimer, out->period_ns, HRTIMER_MODE_REL);
+
+	return 0;
+}
+
+static void vkms_disable_vblank(struct drm_crtc *crtc)
+{
+	struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
+
+	hrtimer_cancel(&out->vblank_hrtimer);
+}
+
+bool vkms_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
+			       int *max_error, ktime_t *vblank_time,
+			       bool in_vblank_irq)
+{
+	struct vkms_device *vkmsdev = drm_device_to_vkms_device(dev);
+	struct vkms_output *output = &vkmsdev->output;
+
+	*vblank_time = output->vblank_hrtimer.node.expires;
+
+	return true;
+}
+
 static const struct drm_crtc_funcs vkms_crtc_funcs = {
 	.set_config             = drm_atomic_helper_set_config,
 	.destroy                = drm_crtc_cleanup,
@@ -17,6 +71,45 @@ static const struct drm_crtc_funcs vkms_crtc_funcs = {
 	.reset                  = drm_atomic_helper_crtc_reset,
 	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
 	.atomic_destroy_state   = drm_atomic_helper_crtc_destroy_state,
+	.enable_vblank		= vkms_enable_vblank,
+	.disable_vblank		= vkms_disable_vblank,
+};
+
+static void vkms_crtc_atomic_enable(struct drm_crtc *crtc,
+				    struct drm_crtc_state *old_state)
+{
+	drm_crtc_vblank_on(crtc);
+}
+
+static void vkms_crtc_atomic_disable(struct drm_crtc *crtc,
+				     struct drm_crtc_state *old_state)
+{
+	drm_crtc_vblank_off(crtc);
+}
+
+static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
+				   struct drm_crtc_state *old_crtc_state)
+{
+	unsigned long flags;
+
+	if (crtc->state->event) {
+		spin_lock_irqsave(&crtc->dev->event_lock, flags);
+
+		if (drm_crtc_vblank_get(crtc) != 0)
+			drm_crtc_send_vblank_event(crtc, crtc->state->event);
+		else
+			drm_crtc_arm_vblank_event(crtc, crtc->state->event);
+
+		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
+
+		crtc->state->event = NULL;
+	}
+}
+
+static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
+	.atomic_flush	= vkms_crtc_atomic_flush,
+	.atomic_enable	= vkms_crtc_atomic_enable,
+	.atomic_disable	= vkms_crtc_atomic_disable,
 };
 
 int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
@@ -31,5 +124,7 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
 		return ret;
 	}
 
+	drm_crtc_helper_add(crtc, &vkms_crtc_helper_funcs);
+
 	return ret;
 }

drivers/gpu/drm/vkms/vkms_drv.c

@@ -54,6 +54,7 @@ static struct drm_driver vkms_driver = {
 	.dumb_map_offset	= vkms_dumb_map,
 	.gem_vm_ops		= &vkms_gem_vm_ops,
 	.gem_free_object_unlocked = vkms_gem_free_object,
+	.get_vblank_timestamp	= vkms_get_vblank_timestamp,
 
 	.name			= DRIVER_NAME,
 	.desc			= DRIVER_DESC,
@@ -100,6 +101,14 @@ static int __init vkms_init(void)
 		goto out_fini;
 	}
 
+	vkms_device->drm.irq_enabled = true;
+
+	ret = drm_vblank_init(&vkms_device->drm, 1);
+	if (ret) {
+		DRM_ERROR("Failed to vblank\n");
+		goto out_fini;
+	}
+
 	ret = vkms_modeset_init(vkms_device);
 	if (ret)
 		goto out_unregister;

drivers/gpu/drm/vkms/vkms_drv.h

@@ -5,6 +5,7 @@
 #include <drm/drm.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_encoder.h>
+#include <linux/hrtimer.h>
 
 #define XRES_MIN    32
 #define YRES_MIN    32
@@ -23,6 +24,9 @@ struct vkms_output {
 	struct drm_crtc crtc;
 	struct drm_encoder encoder;
 	struct drm_connector connector;
+	struct hrtimer vblank_hrtimer;
+	ktime_t period_ns;
+	struct drm_pending_vblank_event *event;
 };
 
 struct vkms_device {
@@ -37,9 +41,20 @@ struct vkms_gem_object {
 	struct page **pages;
 };
 
+#define drm_crtc_to_vkms_output(target) \
+	container_of(target, struct vkms_output, crtc)
+
+#define drm_device_to_vkms_device(target) \
+	container_of(target, struct vkms_device, drm)
+
+/* CRTC */
 int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
 		   struct drm_plane *primary, struct drm_plane *cursor);
 
+bool vkms_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe,
+			       int *max_error, ktime_t *vblank_time,
+			       bool in_vblank_irq);
+
 int vkms_output_init(struct vkms_device *vkmsdev);
 
 struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev);